The United Nations is condemning an attack Monday by the Saudi-led coalition on a hospital in Yemen that local health officials report has left 18 people dead and another 18 wounded. The rural hospital in northwestern Yemen was supported by the charity, Doctors Without Borders.

The attack on the Abs Hospital in Hajjah governorate is the latest of more than 70 health centers that have been damaged or destroyed since March 2015.That is when the Saudi Arabian coalition, an ally of Yemen's government, entered the civil war to prevent a takeover by Houthi rebels.

"I know that both sides have been responsible.In some cases, there has been the use of medical facilities for military purposes as well," she said.

The World Health Organization reports 73 patients were in the hospital at the time of the bombing.They included 23 patients in surgery, 25 in the maternity ward, as well as 13 newborns and 12 patients in the pediatric ward.

WHO spokesman Tarik Jasarevic said all remaining patients and staff have been evacuated from the hospital that was partially destroyed.

"Hajjah governorate is already suffering from serious disruption of health services delivery and shortages of medical staff has continued, ground fighting led to closure of health facilities and departure of medical personnel," she said. "... Hajjah hosts the largest number of IDPs [internally displaced persons] in the country.

In addition to the loss of lives and health workers, she added, "the cessation of the hospital will further deprive access to essential health services among the conflict affected population."

U.N. Secretary-General Ban Ki-moon is calling for a prompt, effective and impartial investigation into the attack.He notes hospitals and medical personnel are explicitly protected under international humanitarian law.